窄通道内热厚材料表面火焰传播的实验研究

利用高度为14 mm的水平窄通道对微重力条件下聚甲基丙烯酸甲酯(PMMA)和聚乙烯(PE)塑料材料表面的火焰传播进行了地面实验模拟研究. 在环境气体氧气浓度为30％和50％、低速气流速度小于15 cm/s的实验条件下, 实验测量了窄通道内材料表面火焰传播速度随气流速度的变化, 它们与微重力下热厚材料火焰传播速度的理论预测结果符合得相当好. 分析认为, 窄通道能够有效地限制浮力对流, 提高燃料表面固相热辐射在火焰传播中的相对作用, 从而提供模拟微重力下热厚材料表面火焰传播特性的实验环境

热薄材料表面火焰传播的三维效应

利用能够限制自然对流的水平窄通道, 对薄材料表面逆风传播火焰的三维效应进行了实验研究, 参数包括气流速度、氧气浓度、燃料宽度等.结果表明, 在足够宽的通道内, 火焰传播随燃料宽度的变化, 表现出随氧气浓度和气流速度的不同而变化的三维特性.侧面热损失和氧气扩散对火焰传播的影响, 在各种氧气浓度和气流速度下, 都限于燃料宽度小于10倍扩散长度

Numerical study on NOx/CO emissions in the diffusion flames of high-temperature off-gas of steelmaking converter

The combustion of high-temperature off-gas of steelmaking converter with periodical change of temperature and CO concentration always leads to CO and NOx over-standard emissions. In the paper, high-temperature off-gas combustion is simulated by adopting counterflow diffusion flame model, and some influencing factors of CO and NOx emissions are investigated by adopting a detailed chemistry GRI 3.0 mechanism. The emission index of NOx (EINOx) decreases 1.7–4.6% when air stoichiometric ratio (SR) increase from 0.6 to 1.4, and it dramatically increases with off-gas temperature at a given SR when the off-gas temperature is above 1500 K. High-concentration CO in off-gas can result in high NOx emissions, and NOx levels increase dramatically with CO concentration when off-gas temperature is above 1700 K. Both SR and off-gas temperature are important for the increase of CO burnout index (BICO) when SR is less than 1.0, but BICO increase about 1% when off-gas temperature increases from 1100 K to 1900 K at SR > 1.0. BICO increases with CO concentration in off-gas, and the influence of off-gas temperature on BICO is marginal. BICO increases with the relative humidity (RH) in air supplied, but it increases about 0.5% when RH is larger than 30%.

辐射交联低烟无卤阻燃材料的研究

聚合物材料以其优异的电绝缘性能而广泛地用作电气绝缘材料。但聚合物材料易燃的缺点促使人们不断地对其进行阻燃性的研究，这种研究过程从添加卤素阻燃剂到非卤素化阻燃逐步完善。本文在阐述了聚合物材料燃烧特性及机理的基础上，介绍了几种常用的无卤阻燃剂的阻燃机理，并对氢氧化铝、氢氧化镁和红磷等应用于聚烯烃复合体系的阻燃性进行了实验研究。结果表明：氢氧化镁的阻燃性优于氢氧化铝，它们达到较好的阻燃效果时的添加量一般为120-150phr。氢氧化镁与红磷复配使用在添加量为90phr时，氧指数为40，阻燃性能十分优秀。材料具有良好的阻燃性能。但与此同时材料的机械性能、电性能及加工性能等都将受到一定程度的破坏。经过选用偶联剂及进行辐射交联改性， 材料的机械性能令人满意。交联度及电气性能的实验。最终得到符合九五科技攻关项目“辐射交联低烟无卤阻燃电线电缆的研究”的预期目标。

辐射交联无卤阻燃绝缘材料的研究

聚合物材料以其优异的电绝缘性能而广泛地用作电气绝缘材料。但聚合物材料易燃的缺点促使人们不断地对其进行阻燃性的研究，这种研究过程从添加卤素阻燃剂到非卤素化阻燃逐步完善。本文在阐述了聚合物材料燃烧特性及机理的基础上，介绍了几种常用的无卤阻燃剂的阻燃机理，并对氢氧化铝、氢氧化镁、红磷及膨胀型阻燃剂等应用于聚乙烯的阻燃进行了实验研究。结果表明：氢氧化铝和氢氧化镁在高添加量时（>150%）,材料具有良好的阻燃性能，但与此同时材料的机械性能、电性能及加工性能等都将受到一定程度的破坏；氢氧化铝和氢氧化镁混合使用时具有协同效应，红磷和氢氧化铝混合使用也具有很好的协同效果；膨胀型阻燃剂（IFR）以较少的添加量（约20%）可使聚乙烯（PE）/乙烯-醋酸乙烯酯（EVA）共混物获得较好的阻燃性能（OI为28），但由于IFR的颗粒太大导致材料的机械性能损失很大，另外材料燃烧时发烟量高及滴流现象还无法解决。 辐射交联技术广泛应用于聚合物材料的改性处理。本文阐述了聚合物辐射交联的一些规律，并研究了电子束辐照PE/EVA时辐照剂量对材料的机械性能、电学性能、凝胶含量及耐老化性能的影响，得出材料的最佳辐照剂量范围为80-120KGy。

Study of an electroosmotic pump for liquid delivery and its application in capillary column liquid chromatography

A packed-bed electroosmotic pump (EOP) was constructed and evaluated. The EOP consisted of three capillary columns packed in parallel, a gas-releasing device, Pt electrodes and a high-voltage power supply. The EOP could generate output pressure above 5.0 MPa and constant flow rate in the range of nl/min to a few mul/min for pure water, pure methanol, 2 mM potassium dihydrogenphosphate buffer, the buffer-methanol mixture and the pure water-methanol mixture at applied potentials less than 20 W The composition of solvent before/after pumping was quantitatively determined by using a gas chromatograph equipped with both flame ionization detector and thermal conductivity detector. It was found that there were no apparent changes in composition and relative concentrations after pumping process for a methanol-ethanol-acetonitrile mixture and a methanol-water mixture. Theoretical aspect of the EOP was discussed in detail. An capillary HPLC system consisting of the EOP, an injection valve, a 15 cm x 320 mum i.d., 5 mum Spherigel C(18) stainless steel analytical column, and an on-column UV detector was connected to evaluate the performance of the EOP. A comparative study was also carried out with a mechanical capillary HPLC pump on the same system. The results demonstrated that the reproducibility of flow rate and the pulsation-free flow property of the EOP are superior to that of mechanical pump in capillary HPLC application. (C) 2004 Elsevier B.V. All rights reserved.

Preparation and characteristics of nonflammable polyimide materials

The thermal and flame-retardant properties of homo- and copolyimides were evaluated. Those containing sulfone linkages in the backbone were found to be more flame retardant. Both properties were dependent on the composition. A polyimide/silica nanocomposite was obtained through sol-gel processing. The effects of the addition of silica an the dispersion, interfacial adhesion, fire resistance, mechanical properties, and thermal stability of the composites were investigated. SEM analysis showed a good dispersion of silica with a diameter of 50-300 nm in the organic matrices. The addition of silica increased the fire retardancy and mechanical properties of the composites. (C) 2000 John Wiley & Sons, Inc.

Controls on suppression of methane flux from a peat bog subjected to simulated acid rain sulfate deposition

The effect of acid rain SO42− deposition on peatland CH4 emissions was examined by manipulating SO42− inputs to a pristine raised peat bog in northern Scotland. Weekly pulses of dissolved Na2SO4 were applied to the bog over two years in doses of 25, 50, and 100 kg S ha−1 yr−1, reflecting the range of pollutant S deposition loads experienced in acid rain-impacted regions of the world. CH4 fluxes were measured at regular intervals using a static chamber/gas chromatographic flame ionization detector method. Total emissions of CH4 were reduced by between 21 and 42% relative to controls, although no significant differences were observed between treatments. Estimated total annual fluxes during the second year of the experiment were 16.6 g m−2 from the controls and (in order of increasing SO42− dose size) 10.7, 13.2, and 9.8 g m−2 from the three SO42− treatments, respectively. The relative extent of CH4 flux suppression varied with changes in both peat temperature and peat water table with the largest suppression during cool periods and episodes of falling water table. Our findings suggest that low doses of SO42− at deposition rates commonly experienced in areas impacted by acid rain, may significantly affect CH4 emissions from wetlands in affected areas. We propose that SO42− from acid rain can stimulate sulfate-reducing bacteria into a population capable of outcompeting methanogens for substrates. We further propose that this microbially mediated interaction may have a significant current and future effect on the contribution of northern peatlands to the global methane budget.

原子吸收光谱法测定膜荚黄芪不同器官矿质元素含量

应用混合酸HNO3-HClO4(4∶1)在常压微沸条件下对膜荚黄芪根系及茎叶样品进行消解,采用原子吸收光谱法测定了膜荚黄芪不同器官即根及茎叶中五种人体必需矿质元素K,Fe,Zn,Mn和Cu含量,并对结果进行了统计分析与比较。该方法标准曲线相关系数为0.997 3~0.999 9,加标回收率为92.88%~109.25%,相对标准偏差(RSD,n=5)为0.393 5%~3.175 2%。方法简单,结果可靠。结果显示,膜荚黄芪根及茎叶中5种矿质元素含量顺序均为K>Fe>Zn>Mn>Cu。膜荚黄芪不同器官矿质元素含量不同,根中富含Fe,Zn,Cu元素,根内Fe含量是茎叶的1.54倍。茎叶中也含有丰富的矿质元素,特别是K和Mn元素。茎叶中K含量是根的1.63倍,这与黄芪的药效相符合。试验结果将为研究矿质元素在黄芪植株中的分布以及矿质元素含量与黄芪药效相关性提供理论依据。

JUTA:一个Java自动化单元测试工具

描述了一个Java自动化的单元测试工具JUTA.JUTA首先调用工具Soot解析单个Java方法的源码,并将源码解析成一个控制流图.在此基础上,采用符号执行的方法分析控制流图上的路径.工具能够自动地产生满足覆盖率标准的程序的测试用例.这种方法产生的所有测试用例都是可执行的,并且一般来说具有较小的测试用例数.如果用户能够合理地给出描述程序错误的断言,框架JUTA能够自动地检查源码中部分特定类型的错误.实验结果表明工具对Java单元代码的动态测试和静态测试均能在可接受的时间内给出有效的结果.

Strengthening carbon deposition of polyolefin using combined catalyst as a general method for improving fire retardancy

Combination of Ni2O3 and solid acid with Bronsted acid sites and Lewis acid sites (such as HZSM-5 and H-beta) could dramatically improve fire retardancy of polyolefin, including polypropylene and linear low-density polyethylene. This is mainly attributed to the formation of a large amount of residual char from degradation products of polyolefin in the intermediate stage of combustion. Thus, the amount of flammable components diffusing into the flame zone was small.

STRUCTURAL EVOLUTION AND COMPOSITION CHANGE IN THE SURFACE REGION OF POLYPROPYLENE/CLAY NANOCOMPOSITES ANNEALED AT HIGH TEMPERATURES

A model experiment was done to clear the formation mechanism of protective layers during combustion of polypropylene (PP)/organically modified montmorillonite (OMMT) nanocomposites. The investigation was focused on the effects of annealing temperature on the structural changes and protective layer formation. The decomposition of OMMT and degradation of PP/OMMT nanocomposites were characterized by means of thermogravimetric analysis (TGA). The structural evolution and composition change in the surface region of PP/OMMT nanocomposites during heating were monitored by means of X-ray photoelectron spectroscopy (XPS), ATR-FTIR and field emission scanning electron microscopy (FESEM).

Perovskite-Like Mixed Oxides (LaSrMn1-x Ni (x) O4+delta, 0 a parts per thousand currency sign x a parts per thousand currency sign 1) as Catalyst for Catalytic NO Decomposition: TPD and TPR Studies

Catalytic NO decomposition on LaSrMn1-x Ni (x) O4+delta (0 a parts per thousand currency sign x a parts per thousand currency sign 1) is investigated. The activity of NO decomposition increases dramatically after the substitution of Ni for Mn, but decreases when Mn is completely replaced by Ni (x = 1.0). The optimum value is at x = 0.8. These indicate that the catalytic performance of the samples is contributed by the synergistic effect of Mn and Ni. O-2-TPD and H-2-TPR experiments are carried out to explain the change of activity. The former indicates that only when oxygen vacancy is created, could the catalyst show enhanced activity for NO decomposition; the latter suggests that the best activity is obtained from catalyst with the most matched redox potentials (in this work, the biggest Delta T and Delta E values).